1. Field of the Invention
The present invention relates to a data memory apparatus for storing data.
2. Description of the Related Art
In recent years, the development of digital apparatuses such as digital videotape recorders ("VTR's") using the digital video ("DV") format, has been promoted, and a data memory apparatus has been used which stores digital data when the error correcting and modifying processing is effected in the course of the digital data processing.
The memory considered for use in the data memory apparatus is a static random-access memory ("SRAM") or dynamic random-access memory ("DRAM"). In the SRAM, the application of one address is sufficient to access one data, and so the access speed is high. Accordingly, in an application to the digital VTR, which requires error correcting and modifying processing having large capacity and high speed, the SRAM is generally used as the memory. On the other hand, the DRAM has a smaller packaging area and is of lower cost than the SRAM, and the possibility of using the DRAM as the memory has been a long felt need.
However, the DRAM has a two-dimensional matrix address space to enable one data to be accessed only when a row address is accessed and thereafter a column address is accessed. Hence when the DRAM is used in the conventional way, the number of access operations leads to a delay in access, raising a problem in that the DRAM has difficulties being used in an application to the digital VTR which requires data processing having large capacity and high speed. Further, in order to perform the error correcting and modifying processing, reliability information for a data block subject to the error correcting processing and management information for performing the modifying processing based on a result of the error correcting processing are needed conventionally, the information pieces are stored in a memory or register which is separate from that for the data block, raising a problem that superfluous memory means is needed.